Snap-action device



May 17, 1955 Filed Aug. 18, 1953 J. w. WELSH ,708,697

SNAP-ACTION DEVICE 2 Sheets-Sheet 1 FIG.5

' iNVENTOR w M4 1.;

I J; ATTNEY I 2,708,697 May 17, 1955 .1. w. WELSH SNAP-ACTION DEVICE Filed Aug. 18, 1953 2 Sheets-Sheet 2 M MM 1 aw INTIENTQR 122; ATTdi-QNEY United States Patent SNAP-ACTION DEVICE James W. Welsh, Summit, N. J., assignor to Signal-Stat Corporation, Brooklyn, N. Y., a corporation of New York Application August 18, 1953, Serial No. 374,918

16 Claims. (Cl. 200-122) This invention relates to snap action electrical switches and, more particularly, to an improved switch of this type in which full contact pressure is maintained or even increased, during the operation of the switch until the instant the contacts make or break so that a square wave make-and-break cycle is obtained.

One of the major problems in switch design is that of obtaining adequate contact life. When the switch contacts open under load, an arc is produced between the separating contacts which tends to burn the contacts or otherwise deteriorate the same. The persistence time of this are is determined by the time taken for the contacts to separate a sufficient distance to break the are. In most types of switches this action is relatively slow, so that the curve of current plotted against time has sloping lines representing the decrease of current flow across the contacts from full load to no load. The sharpness of this slope joining the full load line to the no load line, plotted against time, is a fair measure of the persistence time of the are. If the contacts could be instantaneously moved from a full contact pressure position to a widely separated position, the slope angle would be substantially 90 degrees, there would be little or no arcing, and consequently the life of the contacts would be prolonged.

Actually, in most types of contact switches, of which flashers are a typical example, the contact pressure grad ually decreases before the contacts actually separate. This condition is conducive to the aforementioned arc formation. Even though the final separation of the contacts is effected as a snap action, the prior gradual decrease in contact pressure promotes arcing.

Many expedients have been utilized to overcome this difficulty, including a rearrangement of the switch parameters to achieve rapid breaking or" the circuit and thus a decrease in the time during which the contact pressureis reduced. In addition, many such switches are designed to provide a Wiping action of the contacts prior to the actual separation thereof. However, incorporation'of a wiping action into a switch necessitates the use of a greater amount of operating force to make and break the contacts and, if electrical energy is used for this force, the required current is increased. For switches used in low power applications where power loss must be kept at a minimum, the wiping action must be sacrificed, thus decreasing the contact life. One important application of snap action switches is their use in flasher assemblies in which the activating force is a high resistance wire which expands and contracts to effect the contact operation. This is a typical low power application, so that no wiping action can be incorporated in the switch without sacrificing an undesirable amount of available power.

In my co-pending application, Serial No. 374,976, filed August 18, 1953, for Snap Action Device, I have shown and described a novel snap action vane which may be incorporated in a snap action switch. This vane is provided with an initial bend about a right lineextending across the vane by thinning or deforming the vane along this line in two or more spaced sections of the line, these sections being spaced at their inner ends from the center of the vane and also preferably spaced from the outer ends of the bent line. When such a vane is to be utilized in a snap action switch, such as a flasher, the vane is probably bent about another line, at an angle to the line of initial bending by applying force to the ends of such lines of initial bending. When such force is released, the vane snaps back to its initial bent position, the action closely resembling that of a toggle.

The vane is held in the new deformed position by attaching a high resistance wire or strip at each of its ends to the vane at the ends of the line of initial bending. This high resistance wire or strip thus forcibly holds the vane in a distorted position bent about a line angularly related to the line of initial bending. When the high resistance wire has electric current passing through, it heats and expands. During the expansion of the wire, a point is reached at which the tension exerted by the wire is over-balanced by the kinetic energy of the vane stored therein by bending the latter from its initial bent condition. At this point, the vane snaps back to its initially bent condition.

As described in said co-pending application, the vane has a mounting member secured thereto at a point in an elliptical line representing the distribution of stresses adjacent the vane center due to the initial bending or deformation of the vane. This mounting member extends across the high resistance wire and carries a contact cooperative with a contact carried by a high resistance wire. When the vane is in the deformed position, in which it is held by the contracted high resistance wire, these two contacts are in engagement, so that current from a source of electric power connected to a contact carried by the mounting member flows in parallel paths through the high resistance wire, through the vane, and thence to the other terminal of the current source. When the vane snaps back to its initial condition, as a result of heating and expansion of the wire, the contacts separate and the high resistance wire then cools and contracts. During such contraction, the force exerted by the wire overbalances the force tending to maintain the vane in its initially bent condition, and the resultant toggle action snaps the vane to the deformed condition reengaging the contact carried by the resistance wire with the contact carried by the mounting member for the vane. The electrical circuit is thus reclosed and the cycle repeats.

In accordance with the present invention, an arrangement of this type is provided in which the two contacts are held in full pressure engagement, or even under increasing pressure, during the time the resistance wire is heating and expanding and right up to the instant that the vane snaps back to its present condition. Thus, there is no reduction of contact pressure during the initial part of the switch opening movement or cycle and full pressure is maintained between the contacts uritil they are snapped apart by the snap action of the vane in restoring itself to its preset deformation.

More specifically, the switch parameters are so selected that, when the contacts are engaged and up to the time that the snap action takes place, the resistance wire is depressed at its center toward the' vane, so that the center of the wire exerts a force component in the direction of the contact carried by the vane mounting means. By proper selection of the switch parameters, this contact pressure effecting force may be made to increase during the expansion of the resistance wire so that at least full contact pressure is maintained up to the instant the snap action of the vane occurs.

At such instant, the contacts are snapped apart, thus instantaneously moving the contacts from the full pressure engaged position to a widely separated circuit breaking position. Thereby, with the invention arrangement, a plot of the current flowing across the contacts versus time will essentially resemble a square and there will be practically no slope to the lines connecting the full current portion of the curve to the no portion of the curve.

For an understanding of the invention principles, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawing.

In the drawing:

Fig. 1 is a perspective view of a snap action vane constructed in accordance with the disclosure of my said copending application and having a mounting member secured thereto;

Fig. 2 is a perspective view of a snap action switch embodying the present invention;

Fig. 3 is a sectional view taken on the line 3--3 of Fig. 2;

Fig. 4 is a cycle diagram used in explaining the operation of the invention switch;

Fig. 5 is an oscillograph made with the invention switch, showing current plotted against time for substantially one complete cycle of switch operation; and

Figs. 6a through 6h are diagrams graphically illustrating the operation of the invention switch.

Referring to Fig. 1, which is substantially identical with Fig. 10 of my said co-pending application, a snap action vane 10 is illustrated which is identical with that shown and described in said co-pending application. As described therein, vane 10 is preferably made of relatively thin spring metal, with consideration being given to its spring factor, stillness, temperature coefficient, and the like, in accordance with the desired rate of operation of the snap action.

To provide an initial set to vane 10 and to give the same some depth so that it will resemble a beam in its action, the vane 10, which is shown as a substantially rectangular vane, is deformed or thinned along a diagonal interconnecting corners 11 and 12. This vane deformation is preferably efiected by linearly embossing the vane along the line 11-12 in two elongated spaced portions or bosses 15. It will be noted that the bosses 15 have their inner ends disposed substantially equal distances from the center of vane 10 so that the center area of the vane is left unmarred. As explained insaid co-pending application, this greatly prolongs the life of vane 19 by removing the stress concentration from the center to a pair of points on bosses 15-. If the deformation lines apex on line 1112. When vane bending forces are applied to the end of lines 1112', and the value of these forces equals or over-balances the inherent tendency of the vane to stay in its preset condition, the vane snaps into a new bend or deformed position, forming another shallow V along the other diagonal 1617. When the forces at points 11 and 12 are decreased to a point where they are overbalanced by the kinetic energy stored in vane 10 due to such distorting force, the vane snaps back to a position bent along the line 11-12.

Photographs, taken with polarized light, of a transparent vane formed in this manner show lines of force in the unmarred. center area of the vane which comprise elliptical bands having radii centercdonthe vane center. If. the vane is secured or supported at a pointon one of these elliptical stress; loch, the; stress pointsv on. the, vane during application of bending force at corners 11 and 12 occur within the length of bosses 15. Thus, the stresses are removed from the center area and distributed between two points spaced from the center. This greatly prolongs the period before fatigue takes place in the stressed section of the vane. As described in said copending application, advantage is taken of this fact by supporting the vane by securing the latter, mechanically and electrically, at a point of one of such elliptical lines of force, to a relatively rigid electrically conductive metal mounting member 20. The point of attachment of the mounting member to the vane acts as a pivot point for the vane during its snap action, and is preferably spaced lateraily of the line 11--12.

When the vane is used to form a snap action switch, the bending stresses may be conveniently applied to points 11 and 12 by means of a high resistance wire or strip 3% secured electrically and mechanically to these Lil corners of the vane. For this purpose, the points 11 and 12 are bent downwardly as illustrated in Fig. l, and the ends of wire or strip 30 are secured thereto, as by welding or brazing, at 31 and 32, while the vane is bent along the line 1617, so that the wire in its cold or contracted position holds the vane deformed into a V having its apex along lines 16 and 17. If Wire 30 has electric current passed therethrough, it expands and, as the wire force is overbalanced by the restoring kinetic energy built up in vane 10, the vane snaps back to its initially bent condition along the line 11 and 12.

An arrangement for utilizing this action is illustrated in Figs. 2 and 3 which show the invention snap action switch. The center section 21 of mounting member 20 has a band 23 of insulation wrapped thereon and a band 24 of conductive metal is wrapped around band '23. Band 2d has a contact point 25 electrically and mechanically secured thereto on line with the intersection of mounting member 2% and wire 31 The Wire 31 has a contact point 35 electrically and mechanically secured to its mid-section for cooperation with contact 25.

The free end of mounting member 29 is mechanically secured to a dielectric base as by a rivet ll electrically connecting the outer end 26 of member 29 to an electrically conductive prong or terminal 42 on base 49. Another electrically conductive terminal, not shown, is electrically connected by a conductive strip 43 to band 24.

Referring more particularly to Fig. 2, a source of current, such as a grounded battery 44, is electrically connected through a load 45 to conductor 43 and thus to band 24 v and contact point 25 (Fig. 3). The prong 42 connected electrically to end 26 of conductive bracket or mounting member 2%} is electrically connected by a conductor 46 to an adjustable. resistance 47 electrically connected, through a switch 48, to ground. or the other terminal of battery 44.

Referrim more particularly to Fig. 3 the switch para neters are so selected that, in the contracted or. cooled condition of. wire 3 vane it} is stressed to bend about line lfi17 so that contacts 25 and 35 are engaged, and the relation of section 21 of bracket 29 to vane lit and wire 30 is so selected that the center part of wire 3%, carrying contact 35, is forced inwardly toward vane it}. The wire thus assumes a shallow V as shown in Fig.

3, and the tension of wire 3% thus increases the force with which contacts 25 and 35 are held engaged.

When switch 48 is closed, current flows from battery 44-through load 45, which may be one or more. lamps, conductor 43, band 24 and contact point 25 into contact point 35 at the midpoint of wire 3i}.- At this midpoint, the current branches through both halves of wire 30,, in parallel, and flows into vane 10: at points 31 and. 32. The current flows. through. conductive metal vane 10 into conductive metal mounting member or bracket 26, and thus through rivet 41. into prong; 42

and through conductor. 46, resistance 47, and switch 48 to the other side of the current source. The current flowing through wire 30 causes the latter to rapidly heat and expand, this wire preferably being Nichrome wire. As wire 30 expands and thus lengthens, the force exerted by the wire is finally overbalanced by the kinetic energy stored in vane and the latter snaps to its initial or restored uniplanar or flat position. This vane movement pulls wire 30 downwardly relatively to bracket 20, and snaps contacts 25 and 35 apart to break the electrical circuit. The wire 30 then cools and contracts. As the force exerted by the contracting wire overbalances the force tending to maintain vane 10 in its restored position, the vane again snaps to a position bent along line 16-17 wherein wire 30 snaps toward bracket 20 to reengage contacts and 35. The cycle then repeats. I

As explained at the beginning of this description, the invention arrangement is so designed that the contact pressure between contacts 25 and 35 is maintained at at least full value until the vane snaps to its restored position. Thereby, arcing of the contacts is substantially eliminated. The explanation of this operation will be made with particular reference to Figs. 4, 5, and 6a through 6h.

Fig. 4 is a diagrammatic illustration of one operating cycle of the invention switch with current flow across the contacts being plotted in a vertical direction and time. in a horizontal direction. Line 50 represents this current, with section 51 of the line indicating full current and section 52 no current, as when the switch is open. Section 53 of line 50 is the curve representing the decrease in current from full value to no current flow and vice versa.

Referring to Fig. 5, which is an oscillograph taken with the invention switch as shown in Figs. 2 and 3, the transition section 53 of line 50 during the circuit closing movement is substantially perpendicular to sec tions 51 and 52. The transition section 53 to the right of Fig. 5 approaches the vertical but actually has a very small and substantially infinitesimal slope. Practically speaking, the illustrated current wave amounts to a square wave.

Referring now to Figs. 6a through 6h, the action of the invention switch in maintaining full contact pressure until the circuit break point is reached will be described as graphically illustrated. Before proceeding to this description, it should be mentioned that the mounting of contact 35 at the midpoint of wire has several important advantages. In the first place, the resistance is decreased due to the parallel circuits through wire 30. This enables the use of a wire rather than a ribbon for the high resistance element, which facilitates the proper expansion. In the second place, this contact position is utilized to increase the pressure in wire 30, thus assuring a faster snap actionat'the end of a cycle. A third advantage is that this mounting of contact in effect provides lever arms between the center of the vane and the vane mounting point which comprise springs storing kinetic energy.

Referring to Figs. 6a through 6h, the relatively fixed mounting point of member 20 on vane 10 is represented by the line F carrying the contact point 25. The lines a through e are reference lines graphically illustrating the lengthening and contracting of wire 30. The lines 0-7 are scale lines indicating vertical movement of the ends of wire 30 relative to the fixed reference line F during movement of vane 10. The angle B is proportional to the vane deflection. This angle is also indicative of the contact pressure.

As shown, in the contracted position of wire 39 illustrated in Fig. 6a, the wire is bent into a shallow inverted V so that .the force of thewire tends to increase the pressure between contacts'25 and 35, the wire 30 acting as apressure increasing'spring In Fig. 6a, wire 30 is cool and is just about to be heated. The vane apex is in an elevated condition illustrated by point M due to the mechanical advantage provided when vane 10 is secured at a stress loci point to bracket 20. The vane center is also raised due to the stress imparted thereto by the upward bending of wire 30 to increase the contact pressure. Wire 30 is contracted to its smallest length as indicated by its ends lying on lines AA. As the center of vane 10 is high, a small force in the wire will hold the vane due to the relatively large angle B of the toggle joint arrangement.

As the wire starts to heat due to a flow of current therethrough, the parts assume the position of Fig. 6b. Wire 30 has increased in length, by expansion to lines BB, and the center section of vane 10 is lowered to the line N due to flattening of the vane adjacent to its center sections. Wire 30 upon elongating tends to raise its ends but its center, being higher than its ends, as previously explained, is lower in Fig. 5b than in Fig. 5a thus giving an overall lowering of the vane ends from line 4 to a position between lines 4 and 5. The lowering of the vane ends increases angle B thus increasing the contact pressure.

In Fig. 6c, wire 30 has expanded so that its ends are on the lines C-C. The center section of vane 10,has moved down to line 0 and is approaching a fiat condition, so that its downward movement diminishes. However, the stored energy in the vane decreases, thus providing a new angular relationship. The pressure on contacts 25 and 35 remains substantially the same as in Fig. 6b. The wire relationship also remains about the same as in Fig. 6b. (Angle B becomes smaller so that the tension in wire 30 increases.)

In Fig. 6d, the wire has expanded so that its ends are at the lines D-D, vane 10 is approaching a flat condition, and wire 30 is under great stress. The vane center has lowered slightly. The contact pressure has increased due to the decrease in angle B and the vane is about to snap to its restored condition.

Fig. 62 shows the relation of parts immediately after such snapping of the vane to change the apex of the V from line 16-17 to line 11-12. The relationship of wire 30 to the mounting 20 has changed, due to the snapping of vane 10, thus snapping open contacts 25 and 35 to break the circuit. The wire 30 is essentially the same length as in Fig. 6d, and angle B is quite small.

In Fig. 6f, wire 30 is contracting to build up pressure in the vane and increase the angle B. The vane angle is decreasing and the result is a build-up in pressure in wire 30, which has moved slightly in an upward direction. However, as the vane center is moving more than the wire, the resultant movement of wire 30 is toward line F representing bracket 20.

In Fig. 6g, wire 30 is still contracting but is moving towards bracket 20 due to the diminishing of the upward movement of the vane center as it approaches the Hat condition. The stress in wire 30 has increased and the movement of the parts begins to accelerate. Angle B is increasing, thus building up kinetic energy in vane 10.

Fig. 6h illustrates a position where wire 30 has contracted even further than the position shown in Fig. 63 and vane 10 is about to snap to a bend along lines 1617 to assume the position diagrammatically illustrated in section 6.

It will thus be seen that the invention arrangement provides a snap action switch in which the contact pressure is fully maintained or even increased during the opening movement of the switch, and up to a point where the contacts are snapped to the separating position. While the arrangement for effecting this formation may appear comparatively simple, it has numerous important advantages in increasing the life of the contacts clue to the substantial elimination of arcing between the contacts.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventions principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

I claim:

1. A snap action electric switch comprising, in combination, a dielectric base; a substantially fiat vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an expansible high resistance electric conductor secured at each end to said vane adjacent the outer ends of said deformation, under tension and parallel to said deformation, to bend said vane about a line bisectin'g said deformation at an angle of substantially 90 degrees; means mounting said vane at a point spaced laterally from said deformation whereby, under bending stresses periodically applied to and released from said L value by, respectively, contraction and expansion of said conductor to effect snapping of the vane between a bending-stress-deformed and restored initial preset position, the vane will pivot about such mounting point; a first contact mounted on said conductor intermediate its ends; a second contact fixed relative to said mounting point and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position; and means, including said contacts operable to complete an electric current carrying circuit through said conductor to heat and expand the same.

2. A snap action electric switch comprising, in combination, a dielectric base; a substantially flat vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; and with curvilinear stress concentration loci concentric with the vane center; an expansible high resistance electric conductor secured at each end to said vane adjacent the outer ends of said deformation, under tension and parallel to said deformation, to bend said vane about a line bise'cting said deformation at an angle of substantially 96 degrees; means mounting said vane at a point on one of said loci spaced laterally from said deformation and extending across the central area of the vane outwardly of said resistance conductor, whereby, under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said conductor to effect snapping of the vane between a bending-stress-deformed and restored initial preset position, the vane will pivot about such mounting point; a first Contact fixed relative to said mounting point; a second contact secured to said conductor intermediate the conductor ends and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position; and means, including said contacts operable to complete an electric current carrying circuit through said conductor to heat and expand the same.

3. A snap action electric switch comprising, in combination, a dielectric base; a substantially fiat vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an expansible high resistance electric conductor secured at each end to said vane adjacent the outer ends of said deformation, under tension and paralhe] to said deformation, to bend said vane about a line bisecting said deformation at an angle of substantially 90 degrees; means mounting said vane at a pointspac'ed laterallvfr'oni said deformation, whereby, under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said conductor to (effect snapping of the vane between a bending-stress-deformed and restored initial preset position, the vane will pivot about such mounting point; said conductor, in one of said vane positions, lying along said vane and, in the other of said vane positions, having an intermediate portion spaced from the vane; a first contact at a fixed distance from said vane; a second contact secured to said conductor intermediate its ends and engaged with said first contact in one of said van-e positions; and means, including said contacts operable to complete an electric current carrying circuit through said conductor to heat and expand the same.

4. A snap action electric switch comprising, in combination, a substantially flat and rectangular vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross along a diagonal, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an expansible high resistance electric conductor secured at each end to said vane adjacent the outer ends of said deformation, under tension and extending along said deformation, to bend said vane about the other diagonal of said vane; means mounting said vane at a point spaced laterally from said deformation, whereby, under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said conductor to effect snapping of the vane between a bending-stressdeformed and restored initial preset position, the vane will pivot about such mounting point; a first contact fixed relative to said mounting point; a second contact secured to said conductor intermediate the conductor ends and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position; and means, including said contacts operable to complete an electric current carrying circuit through said conductor to heat and expand the same.

5. A snap action electric switch comprising, in combination, a dielectric base; a substantially flat vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an expansible high resistance electric conductor secured ate'ach end to said vane adjacent the outer ends of said deformation, under tension and parallel to said deformation, to bend said vane about a line bisccting said deformation at an angle of substantially degrees; an electrically conductive mounting member secured at one end to said vane at a point spaced laterally from said deformation and extending across the central area of the vane outwardly of said resistance conductor, whereby, under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said conductor to effect snapping of the vane between a bending-stress-de'formed and restored initial preset position, the vane will pivot about such mounting point; the other end of said mounting member secured to said dielectric base; a first contact mounted on the inner side of said mounting member and insulated from the latter; a second contact secured to said conductor intermediate the conductor ends and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position; said conductor, in the restored position of said vane, lying in juxtaposition to said vane and in relatively widely spaced relation to said mounting member; the portion of said mounting member carrying said first contact being spaced fro i said vane a distance such that said contacts when engaged, bias the contact carrying portion of said con ductor toward said sane and inwardly relative to the conductor ends to increase the stress in said conductor to maintain full contact pressure during expansion of said conductor until the vane snaps to the restored condition to separate said contacts; and a pair of terminals on said base respectively connected to said mounting member and said first contact for connection across a source of electricity for flow of current through said conductor to heat and expand the same to relieve the conductor tension for snapping of the vane to its restored position.

6. A snap action electric switch comprising, in combination, a dielectric base; a substantially flat vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; and with curvilinear stress concentration loci concentric with the vane center; an expansible high resistance electric conductor secured at each end to said vane adjacent the outer ends of said deformation, under tensi n and parallel to said deformation, to bend said vane about a line bisecting said deformation at an angle of substantially 90 degrees; an electrically conductive mounting member secured at one end to said vane at a point on one of said loci spaced laterally from said deformation and extending across the central area of the vane outwardly of said resistance conductor, whereby under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said conductor to effect snapping of the vane between a bending-stress-deformed and restored initial preset position, the vane will pivot about such mounting point; the other end of said mounting member being secured to said dielectric base; a first contact mounted on the inner side of said mounting member and insulated from the latter; a second contact secured to said conductor intermediate the conductor ends and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position; said conductor, in the restored position of said vane, lying in jutaposition to said vane and in relatively widely spaced relation to said mounting member; the portion of said mounting member carrying said first contact being spaced from said vane a distance such that said contacts, when engaged, bias the contact carrying portion of said conductor toward said vane and inwardly relative to the conductor ends to increase the stress in said conductor to maintain full contact pressure during expansion of said conductor until the vane snaps to the restored condition to separate said contacts; and a pair of terminals on said base respectively connected to said mounting member and said first contact for connection across a source of electricity for flow of current through said conductor to heat and expand the same to relieve the conductor tension for snapping of the vane to its restored position. a l

7. A snap action electric switch comprising in combination, a dielectric base; a substantially flat vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an expansible high resistance electric conductor secured at each end to said vane adjacent the outer ends of said deformation, under tension and parallel to said deformation, to bend said vane about a line bisecting said deformation at an angle of substantially 90 degrees; an electrically conductive mounting member secured at one end to said vane at a point spaced laterally from said deformation and extending substantiallyparallel to said vane across the midpoint of said conductor and outwardly of the latter, whereby, under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said conductor to effect snapping of the vane between a bending-stress-deformed and restored initial preset position, the vane will pivot about such mounting point; the other end of said mounting member being secured to said dielectric base; a first contact mounted on the inner side of said mounting member and insulated from the latter; a second contact secured to substantially the midpoint of said conductor and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position; said conductor, in the restored position of said vane, lying in juxtaposition to said vane and in relatively widely spaced relation to said mounting member; the portion of said mounting member carrying said first contact being spaced fr m said vane a distance such that said contacts, when engaged, bias the contact carrying portion of said conductor toward said vane and inwardly relative to the conductor ends to increase the stress in said conductor to maintain full contact pressure during expansion of said conductor until the vane snaps to the restored condition to separate said contacts; and a pair of terminals on said base respectively connected to said mounting member and said first contact for connection across a source of electricity for flow of current through said conductor to heat and expand the same to relieve the conductor tension for snapping of the vane to its restored position.

8. A snap action electric switch comprising, in combination, a dielectric base; a substantially flat vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an expansible high resistance electric conductor secured at each end to said vane adjacent the outer ends of said deformation, under tension and parallel to said deformation, to bend said vane about a line bisecting said deformation at an angle of substantially 90 degrees; an electrically conductive mounting member secured at one end to said vane at a point spaced laterally from said deformation and extending across the central area of the vane outwardly of said resistance conductor, whereby, under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said conductor to effect snapping of the vane between a bending-stress-deformed and restored initial preset position, the vane will pivot about such mounting point; the other end of said mounting member being secured to said dielectric base; a first contact mounted on the inner side of said mounting member and insulated from the latter; a second contact secured to said conductor intermediate the conductor ends and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position; said conductor, in the restored position of said vane, lying in juxtaposition to said vane and in relatively widely spaced relation to said mounting member; the portion of said mounting member carrying said first contact being spaced from said vane a distance such that said contacts, when engaged, bias the contact carrying portion of said conductor toward said vane and inwardly relative to the conductor ends to increase the stress in said conductor to maintain full contact pressure during expansion of said conductor until the vane snaps to the restored condition to separate said contacts; and a pair of terminals on said base respectively connected to said mounting member and said first contact for connection across a source of electricity for flow of current through said conductor in two parallel paths to said vane and thence to said mounting member to heat and expand the condoctor to relieve the conductor tension for snapping of the vane to its restored position.

9. A snap actionelectric switch comprising, in combination, a dielectric base; a substantially flat vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; and with curvilinear stress concentration loci concentric with the vane center; an expansible high resistance electric conductor secured at each end to said vane adjacent to the outer ends of said deformation, under tension and parallel to said deformation, to bend said vane about a line bisecting said deformation at an angle of substantially 90 degrees; an electrically conductive mounting member secured at one end to said vane at a point on one of said loci spaced laterally from said deformation and extending across the central area of the vane outwardly of said resistance conductor, whereby, under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said conductor to effect snapping of the vane between a bending-stress-deformed and restored initial preset position, the vane will pivot about such mounting point; the other end of said mounting member being secured to said dielectric base; a first contact mounted on the inner side of said mounting member and insulated from the latter; a second contact secured to said conductor intermediate the conductor ends and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position of said vane, lying in juxtaposition to said vane and in relatively widely spaced relation to said mounting member; the portion of said mounting member carrying said first contact being spaced from said vane a distance such that said contacts, when engaged, bias the contact carrying portion of said conductor toward said vane and inwardly relative to the conductor ends to increase the stress in said conductor to maintain full contact pressure during expansion of said conductor until the vane snaps to the restored condition to separate said contacts; and a pair of terminals on said base respectively connected to said mounting member and said first contact for connection across a source of electricity for flow of current through said conductor in two parallel paths to said vane and thence to said mounting member to heat and expand the conductor to relieve the conductor tension for snapping of the vane to its restored position.

10. A snap action electric switch comprising, in combination, a dielectric base; a substantially fiat vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an expansible hi h resistance electric conductor secured at each end to said vane ad acent the outer ends of said deformation, under tension and parallel to said deformation, to bend said vane about a line bisecting said deformation at an angle of substantially 90 degrees; an electrically conductive mounting member secured at one end to said vane at a point spaced laterally from said deformation and extending substantially parallel to said vane across the midpoint of said conductor and outwardly of the latter, whereby, under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said conductor to effect snapping of the vane between a bending-stress-deformed and restored initial preset position, the vane will pivot about such mounting point; the other end of said mounting member being secured to said dielectric base; a first contact mounted on the inner side of said mounting member and insulated from the latter; a second contact secured to substantially the mid-point of said conductor and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position; said conductor, in the restored position relatively Widely spaced relation to said mounting member; the portion of said mounting member carrying said first contact being spaced from said vane a distance such that said contacts, when engaged, bias the contact carrying portion of said conductor toward said vane and inwardly relative to the conductor ends to increase the stress in said conductor to maintain full contact pressure during expansion of said conductor until the vane snaps to the restored condition to separate said contacts; and a pair of terminals on said base respectively connected to said mounting member and said first contact for connection across a source of electricity for flow of current through said contacts and in parallel through both halves of the conductor to said vane and thence to said mounting member to heat and expand the conductor to relieve the conductor tension for snapping of the vane to its restored position.

11. A snap action electric switch comprising, in combination, a dielectric base; a substantially flat and rectangular vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross along a diagonal, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an ex pansible high resistance electric conductor secured at each end to said vane adjacent the outer ends of said deformation, under tension and extending along said deformation, to bend said vane about the other diagonal of said vane; an elongated electrically conductive mounting member secured at one end to said vane at a point spaced laterally from said deformation and extending across the central area of the vane outwardly of said resistance conductor, whereby, under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said conductor to eifect snapping of the vane between a bend-stress-deforrned and restored initial preset position, the vane will pivot about such mounting point; the other end of said mounting member being secured to said dielectric base; a first contact mounted on the inner side of said mounting member and insulated from the latter; a second contact secured to said conductor intermediate the conductor ends and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position; s'aid conductor, in the restored position of said vane, lying in juxtaposition to said vane and in relatively widely spaced relation to said mounting member; the portion of said mounting member carrying said first contact being spaced from said vane a distance such that said contacts, when engaged, bias the contact carrying portion of said conductor toward said vane and inwardly relative to the conductor ends to increase the stress in said conductor to maintain full contact pressure during expansion of said conductor until the vane snaps to the restored condition to separate said contacts; and a pair of terminals on said base respectively connected to said mounting member and said first contact for connection across a source of electricity for flow of current through said conductor to heat and expand the same to relieve the conductor tension for snapping of the vane to its restored position.

12. A snap action electric switch comprising, in combination, a dielectric base; a substantially flat and rectangular vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross along a diagonal, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; and with curvilinear stress concentration loci concentric with the vane center; an expansible high resistance electric conductor secured at each end to said vane adjacent the outer ends of said deformation, under tension and extending of said vane, lying in juxtaposition to said vane and in stone i deformation, to bend a vane a out he other diagonal of said vane; an elongated electrically conductive mounting member secured at one end to said vane at a point on one of said loci spaced laterally from said deformation and extending across the central area of the vane outwardly of said resistance conductor, whereby, under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said conductor to effect snapping of the vane between a bending-stress-deformed and restored initial preset position, the vane will pivot about such mounting point; the other end of said mounting member being secured to said dielectric base; a first contact mounted on the inner side of said mounting member and insulated from the latter; a second contact secured to said conductor intermediate the conductor ends and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position; said conductor, in the restored position of said vane, lying in juxtaposition to said vane and in relatively widely spaced relation to said mounting member; the portion of said mounting member carrying said first contact being spaced from said vane a distance such that said contacts, when engaged, bias the contact carrying portion of said conductor toward said vane and inwardly relative to the conductor ends to increase the stress in said conductor to maintain full contact pressure during expansion of said conductor until the vane snaps to the restored condition to separate said contacts; and a pair of terminals on said base respectively connected to said mounting member and said first contact for connection across a source of electricity for flow of current through said conductor to heat and expand the same to relieve the conductor tension for snapping of the vane to its restored position.

13. A snap action electric switch comprising, in combination, a dielectric base; a substantially flat and rectangular vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross along a diagonal, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an expansible high resistance electric conductor secured at each end to said vane adjacent the outer ends of said deformation, under tension and extending along said deformation, to bend said vane about the other diagonal of said vane; an elongated electrically conductive mounting member secured at one end to said vane at a point spaced laterally from said deformation and extending substantially parallel to said vane across the midpoint of said conductor and outwardly of the latter, whereby, under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said conductor to effect snaping of the vane between a bending-stress-deformed and restored initial preset position, the vane will pivot about such mounting point; the other end of said mounting member being secured to said dielectric base; a first contact mounted on the inner side of said mounting member and insulated from the latter; a second contact secured to said conductor intermediate the conductor ends and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position; said conductor, in the restored position of said vane, lying in juxtaposition to said vane and in relatively widely spaced relation to said mounting member; the portion of said mounting member carrying said first contact being spaced from said vane a distance such that said contacts, when engaged, bias the contact carrying portion of said conductor toward said vane and inwardly relative to the conductor ends to increase the stress in said conductor to maintain full contact pressure during expansion of said conductor until the vane snaps to the restored condition to separate said contacts; and a pair of terminals on said base respectively connected to said mounting member and said first contact for connection across a source of electricity ".14 for flow of current through said contacts and in parallel through both halves of the conductor to said vane and thence to said mounting member to heat and expand the conductor to relieve the conductor tension for snapping of the vane to its restored position.

14. A snap action electric switch comprising, in combination, a dielectric base; a substantially flat and rectangular vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross along a diagonal, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; and with curvilinear stress concentration loci concentric with the vane center; the vane corners at the end of said diagonal being bent from the general plane of the vane; an expansible high resistance electric conductor secured at each end to the convex outer surfaces of said bent corners, under tension and extending along said deformation, to bend said vane about the other diagonal of said vane; an elongated electrically conductive mounting member secured at one end to said vane at a pointon one of said loci spaced laterally fromsaid deformation and extending substantially parallel to said vane across the midpoint of said conductor and outwardly of the latter, whereby, under bending stresses periodically applied to and released from said vane, by, respectively, contraction and expansion of said conductor to effect snapping of the vane between a bending-stress-deformed and restored initial preset position, the vane will pivot about such mounting point; the other end of said mounting member being secured to said dielectric base; a first contact mounted on the inner side of said mounting member and insulated from the latter; a second contact secured to substantially the midpoint of said conductor and engaged with said first contact when said conductor is contracted to bend said vane to the stress-deformed position; said conductor, in the restored position of said vane, lying in juxtaposition to said vane and in relatively widely spaced relation to said mounting member; the portion of said mounting member carrying said first contact being spaced from said vane a distance such that said contacts, when engaged, bias the contact carrying portion of said conductor toward said vane and inwardly relative to the conductor ends to increase the stress in said conductor to maintain full contact pressure during expansion of said conductor until the vane snaps to the restored condition to separate said contacts; and a pair of terminals on said base respectively connected to said mounting member and said first contact for connection across a source of electricity for flow of current through said contacts and in parallel through both halves of the conductor to said vane and thence to said mounting member to heat and expand the conductor to relieve the conductor tension for snapping of the vane to its restored position.

15. A snap action electric switch comprising, in combination, a dielectric base; a substantially flat and rectangular vane of electrically conductive resilient material having a substantially linear preset deformation extending thereacross along a diagonal, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; and with curvilinear stress concentration loci concentric with the vane center; the vane corners at the end of said diagonal being bent from the general plane of the vane; an expansible high resistance electric wire secured at each end to the convex outer surfaces of said bent corners under tension and extending along said deformation, to bend said vane about the other diagonal of said vane; an elongated electrically conductive mounting member secured at one end of said vane at a point on one of said loci spaced laterally from said deformation and extending subsantially parallel to said vane across the midpoint 15 of said wire and outwardly of the latter, whereby, under bending stresses periodically applied to and released from said vane by, respectively, contraction and expansion of said Wire to effect snapping of the vane between a bending-stress-deformed and restored initial preset position, the vane will pivot about such mounting point; the other end of said mounting member being secured to said dielectric base; a first contact mounted on the inner side of said mounting member and insulated from the latter; a second contact secured to substantially the midpoint of said wire and engaged with said first contact when said Wire is contracted to bend said vane to the stress-deformed position; said wire, in the restored position of said vane, lying in juxtaposition to'said vane and in relatively widely spaced relation to said mounting member; the portion of said mounting member carrying said first contact being spaced from said vane a distance such that said contacts, when engaged, bias the contact carrying portion of said wire toward said vane and inwardly relative to the wire ends to increase the stress in said wire to maintain full contact pressure during expansion of said wire until the vane snaps to the restored condition to separate said contacts; and a pair of terminals on said base respectively connected to said mounting member and said first contact for connection across a source of electricity for flow of current through said contacts and in parallel through both halves of the Wire to said vane and thence to said mounting member to heat and expand the wire to relieve the wire tension for snapping of the vane to its restored position, all occurrences.

16. A snap action switch as claimed in 15 in which said mounting member has an end portion secured to said vane, an intermediate elongated portion olfset outwardly from said end portion and extending across said wire, and an outer end portion offset outwardly from said intermediate portion and secured to said base; a dielectric wrapping on said intermediate portion; and a conductive band embracing said wrapping; said first contact being secured to said band.

References Cited in the file of this patent UNITED STATES PATENTS 

